Recovery of Salvageable Metal:
In recent years, there has been a dramatic increase in the volume and variety of solid waste products requiring disposal by both the private and public sectors. Such solid waste products have in the past been burned in open incinerators. However, due to current environmental laws and regulations, open incineration of solid waste has been restricted to a significant extent in many geographic areas and in fact is prohibited in many urban areas today.
Disposal and burial of solid waste products in sanitary landfills is a frequently used alternative disposal method. However, many existing landfills are reaching their capacity and additional replacement clean landfills have not been approved by regulatory agencies and authorities due to existing environmental laws and regulations and due to an actual shortage of land in some geographic areas.
Recovery of salvageable and recyclable metals, of course, reduces the maount of waste products that must be disposed. Apparatus and methods for recovery of salvageable and recyclable components, such as glass, plastics, non-ferrous and ferrous materials, from solid waste products are known in the prior art, e.g., U.S. Pat. Nos. 3,086,718; 3,549,092; 3,659,396; 3,687,062; 3,788,568; 3,790,091; 3,885,744; 3,973,736; 4,020,992; 4,044,956; 4,070,278; 4,083,774; 4,337,900; 4,341,353; 4,362,276; and 4,387,019. Such recovery apparatus and methods proposed recovery of ferrous and non-ferrous metal components from solid waste products both prior to and subsequent to incineration of the solid waste products. However, ferrous and non-ferrous metal components are generally not efficiently or economically recovered by such prior art apparatus and methods.
Particularly, the systems and means for recovering non-ferrous materials that have been proposed to date for separation of non-ferrous metal from incinerated solid waste and ferrous waste components are expensive to build, expensive to operate and resulted in low percentage of recovery of non-ferrous metals. It has been proposed to indiscriminately comminute the non-ferrous metals, along with the ferrous metals and other materials in the incinerated solid waste, and then separate the non-ferrous metal by a float-sink method. Alternatively, it has been proposed to comminute the incinerated solid waste in a cage mill and then separate the non-ferrous metal in a two-stage trommel screen. These methods have been discontinued, however, because of the low efficiency in recovery of non-ferrous metals and the high costs of assembly and operation of the equipment and system.
In addition, the quality of the recovered ferrous and non-ferrous products varies widely due to the incinerated waste product carryover (called "tramp"), and the extreme variability of the moisture content (typically 20 to 75%) in both the pre-incinerated and incinerated waste material.
A need thus exists for a system that will permit efficient and economic recovery of ferrous metal, such as iron and steel, and non-ferrous metal, such as aluminum, from incinerated waste materials including friable carbonaceous incineration byproducts, such as ash. Such a system, should not only permit the recovery of the salvageable ferrous and non-ferrous metal components with relatively low percentage of tramp, but also should reduce the amount of the incineration byproduct, e.g., ash and metal, that must be disposed by conventional disposal such as landfill. As to the latter, the present system allows for reclaim of carbonaceous incineration byproducts for use as ballast for road beds and the like, in addition to efficient and economical recovery of ferrous and nonferrous metals.
Crusher Devices:
Various types of devices for crushing and communication have been known for decades. These include hammermills, cage mills, attritors, ball mills and rod mills. These devices have been used to crush and comminute a whole myraid of materials from rock, coal, ores and solid waste to chocolate and paint pigment.
U.S. Pat. No. 2,582,734 discloses one such crusher which has relation as prior art to the presently claimed subject matter. A horizontal roll crusher is disclosed that has a main eccentric gyrated crusher drum positioned between the crushing plate surfaces of a pair of swing jaws. Each swing jaw is supported and resiliently carried by springs and hydraulic shock absorbers. These bias means are designed primarily to provide the function of protecting the swing jaws and the other parts of the crusher against excessive mechanical overload, as well as secondarily to serve the additional function of accurately positioning the swing jaws in accordance with the relative wear of crusher surfaces and in accordance with the desired finest of the crushed product to be produced by the crusher.
Another example of a similar prior art crusher is disclosed in U.S. Pat. No. 1,783,373. A single-roll crusher is disclosed that has a breaker-plate mounted to crush coal, ore and the like in the throat between the breaker plate and the single roll. The improvement there described is a breaker plate in a plurality of sections hanging from a single shaft, each section of which is independently supported and postioned in alignment with the crusher roll. The breaker-plate is urged toward the crusher roll by bias means that permit relief to avoid breakage and cracking when foreign objects, such as large pieces of wood, tramp iron and the like, are delivered to the crusher along with the coal, ore or other material to be crushed. The purpose of the bias means is to avoid breaking or cracking of the backer-plate or crusher roll by "a large foreign body, incapable of being crushed," thereby avoiding the condition that would require stoppage of the crusher and dismantling the machine until a new backer-plate or roll could be supplied.
In these prior art crushers, the bias means avoided damage to the machine upon the encounter of the rare, foreign body that was incapable of being crushed. There is no suggestion that the bias means exert such pressure so as to selectively comminute certain materials within a mix of materials while allowing associated materials to remain substantially uncomminuted. To the contrary, the pressure exerted by the bias means is purposely set very high so as to indiscriminately comminute all of the materials encountered except for those few pieces incapable of being crushed, where breaking or cracking the machine would result. Also, there is no suggestion in these prior art crushers of regulating the pressure exerted by the bias means to allow efficient comminution of select materials within a mix while avoiding comminution, to the extent possible, of associated materials within the material fed to the crusher.